1. Field of the Invention
The present invention concerns a method of fabricating a superplastically formable strip or a superplastically formable foil from TiAl6V4 with a thickness of no more than 0.9 mm.
2. Background Art
Owing to their good application properties such as very low density, high stability and excellent corrosion resistance, titanium alloys such as TiAl6V4 are used in many industrial branches, for instance aerospace industry, chemical industry, medical engineering and mechanical engineering. According to application, different demands are placed on the titanium alloys as to the specific properties thereof. The workability of materials made of TiAl6V4 is limited, however, since TiAl6V4, which consists of a mixture of the α- and the β-phase, shows exceptionally poor cold forming properties.
Materials made of TiAl6V4 are often brought into the desired final shape by superplastic formation. Depending on the desired final thickness of the material, this requires basic materials of a higher or lower thickness. TiAl6V4 strips or TiAl6V4 foils, respectively, with a thickness less than 1 mm are not commercially available, however. Moreover, the prior-art methods of fabricating such TiAl6V4 strips or TiAl6V4 foils, respectively, are very complex and have more or less considerable drawbacks.
U.S. Pat. No. 4,838,337 discloses a method of fabricating foils from a titanium alloy in which a powder with the desired composition is at first applied to a metal foil by plasma spraying, causing a titanium alloy deposit to form which is then separated from the metal foil by dissolving the metal foil in a solution of nitric acid.
U.S. Pat. No. 4,805,294 discloses a method of fabricating thin foils from a titanium alloy in which a powder with the desired composition is at first applied to a metal foil by plasma spraying, causing a titanium alloy deposit to form which is then separated from the metal foil and rolled to reduce the thickness thereof and to improve the smoothness of the surface. This method is however very complex. Moreover, this method allows fabrication of only very small sizes with partly imperfect micro structures.